1. Field of the Invention
This invention relates generally to drive mechanisms for vehicle sunroofs and, more particularly, to a drive mechanism for a vehicle sunroof having means for detecting the fully open and fully closed positions of the movable roof panel of the sunroof and shutting off the sunroof drive motor when the roof panel reaches either of its limits of movement.
2. Description of the Prior Art
A typical vehicle sunroof of the sliding type usually includes a roof panel which slidably moves beneath the stationary roof portion of the vehicle to reveal an opening in the roof. The movable roof panel usually is mounted on shoes which slidably engage guide rails provided along the sides of the sunroof frame. Movement of the panel is effected, in the case of powered units, by a drive motor which acts through a transmission to drive a pair of push-pull cables, each of which is coupled to the shoes on either side of the sunroof opening.
The drive motor of a powered sunroof is susceptible to overloading and burnout if electrical power continues to be delivered to the motor after the roof panel has reached either of its limits of movement, i.e., either its fully closed or fully open position. In order to prevent such overloading, means usually is provided for detecting the end positions of the roof panel and shutting off the motor when these limits are reached. Limit switches usually are positioned adjacent the path of travel of the roof panel, these switches directly sensing the presence of the panel when it reaches either limit of movement. In installing this type of sunroof, however, it is often quite difficult initially to adjust the positions of the switches relative to the sunroof opening so that they correctly sense the end positions of the slidable roof panel. This is due to the fact that the switches, which must be installed before the roof panel, become concealed once the roof panel has been installed. In most cases, due to manufacturing and assembly inaccuracies, repeated adjustment is required at the time of sunroof installation. This results in excessive manufacturing time for each vehicle. Also contributing to excessive manufacturing time is the necessity of separately installing limit switches and associated connectors--additional parts which augment an already lengthy list of parts for any contemporary automobile.
Another type of roof panel position detector is disclosed in West German Pat. No. 19 06 084, published Oct. 15, 1970. In the sunroof there disclosed, a pinion meshes with one of the sunroof drive cables and is rotated whenever the roof panel moves. A worm gear is mounted on the pinion shaft, and a longitudinally slidably guided, internally threaded collar surrounds and meshes with the worm gear. The collar has two trip cams which actuate adjacent limit switches to control the drive motor when the collar is moved longitudinally by the action of the driven pinion and the engaged threaded surfaces of the worm and collar. This detection mechanism significantly reduces the need for repeated roof panel removal and adjustment, but does not solve other problems associated with sunroof mechanisms. For example, the detection mechanism itself constitutes one more item which requires installation time in the vehicle, occupies additional space in an area where space is at a premium, and requires separate access through the sunroof frame for installation and removal for repair or replacement.